Determination of Iron in Nickel Base Superalloys by Double Endpoints Potentiometric Titration
A double endpoints automatic potentiometric titration method for determination of iron content in nickel base superalloys was established.The platinum electrode is used as the indicator electrode and the potassium dichromate standard titration solution is used as the titrant.The sample is dissolved by hydrochloric acid,nitric acid and perchloric acid.Iron and coexisting interfering elements are separated by ammonia.In the environment with acidity of 10%hydrochloric acid,take sodium tungstate as the indicator,titanium trichloride is used to adjust the solution to blue.Under the set titration procedure and parameters,potassium dichromate standard titration solution is used to titrate to two equivalent points.The volume difference between the two equivalent points is the titration volume of iron consumption,and calculate the iron content.Becides,the instrument parameters,acidity of the titration medium,interference of coexisting elements,and separation conditions of interfering elements were investigated.Under the optimal experimental conditions,test certified reference materials and the method comparision were conducted,and the admissible error complied with rules in HB 5220.29-2008.The relative standard deviations were 0.16%～0.44%.The method avoids the error caused by artificial endpoint determination,and reduces the steps of titrating excessive titanium trichloride in the visual titration.The test operation is simple,the accuracy is high,and the precision is good,which can meet the determination of iron in nickel base superalloys.
potentiometric titrationnickel base superalloysiron content
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